Image sensor chips typically comprise a linear array of photosensors which raster scan an image-bearing document and convert the microscopic image areas viewed by each photosensor to image signal charges. Following an integration period, the image signal charges are amplified and transferred as an analog video signal to a common output line or bus through successively actuated multiplexing transistors.
For high-performance image sensor arrays, a preferred design includes an array of photosensors of a width comparable to the width of a page being scanned, to permit one-to-one imaging generally without the use of reductive optics. In order to provide such a “full-width” array, however, relatively large silicon structures must be used to define the large number of photosensors. One technique to create such a large array is to make the array out of several butted silicon chips. In one design, an array comprises 20 silicon chips, butted end-to-end, each chip having 372 active photosensors spaced at 600 photosensors per inch.
Besides photosensor arrays, there are other types of multi-chip systems useful in recording or making images. In xerographic systems, there can be provided “LED arrays,” meaning chips in which a linear array of a laser emitters are used to discharge imagewise areas on a photoreceptor for xerographic printing purposes. Also, many designs of ink-jet printheads include, on a chip, a series of independently-addressable ink-jet emitters.
Whether an imaging chip is used for recording images or creating images, a common feature in such chips is the use of a shift register, the stages of the shift register being in various possible ways associated with the different “imaging elements” (e.g., photosensors, light emitters, ink-jet emitters, etc.), so that individual imaging elements can be addressed at various times, such as for image input or image readout.
In any multi-chip imaging system, there will be occasions when operating instructions or parameters are desired to be communicated to one or more chips in the system. In the case of a photosensor chip, such parameters may include offset and gain values, or duration of integration times. In other types of imaging chips, the parameters may include operating voltages or temperatures, or pulse durations. In different situations, it may be desired to communicate the same parameter data to all chips in a system, or to direct a parameter to a specific chip in a multi-chip system.
U.S. Published Patent Application 2006/0274174 and U.S. Published Patent Application 2006/0291008 each relate to directing data related to a desired operating parameter, such as a reference voltage level, or photosensor integration time, to a photosensor chip. U.S. patent application Ser. No. 11/588,904, filed Oct. 26, 2006, describes a system for directing image sensor control data, to each of a set of imaging chips using a shared wiring arrangement. In that application, the inputs DIN, PROG, and PCLK represent parts of what is known in the art as a “three-wire programming interface.”